https://www.state.gov/r/pa/prs/ps/2016/05/257733.htm

“SENIOR STATE DEPARTMENT OFFICIAL ONE: I can go ahead and address the funding issue. It’s true that the office that processes FOIA has in fact been underfunded for a number of years. Recognizing that in 2017, there was a one-time request made for additional staff. That took place. Those people were added. Going forward, now we are certainly including additional funding in the funding request for the next few years.”

Not proof, but it’s all I could find in five minutes.